(a) Technical Field
The present invention relates to protecting a high voltage battery in a hybrid electric vehicle. More particularly, it relates to protecting a high voltage battery in a hybrid vehicle by preventing a battery from being overcharged when a motor and/or an inverter system break while the hybrid vehicle travels.
(b) Background Art
Hybrid electric vehicles include as main parts an engine, a transmission, and a motor, in which appropriate power for driving the vehicles are supplied by controlling the conditions of the parts, using a controller.
FIG. 1 shows a diagram schematically illustrating the connection of a battery 10 and a motor 40, which is a driving unit, in a common hybrid electric vehicle. As shown in FIG. 1, the hybrid electric vehicle includes the motor for driving the vehicle as a driving unit, other than an engine.
The motor 40, the driving unit, is connected to a high voltage battery 10 to be supplied with power from the high voltage battery and a DC voltage supplied from the high voltage battery is converted into AC voltage through an inverter system to operate the motor, such as a DC/DC converter 20 and a controller circuit 30, as may be appreciated by those skilled in the art.
Since the motor and the inverter system are operated by the power from the high voltage battery, the efficiency of the motor and the inverter system are considered to be more important. Accordingly, an interior permanent magnet synchronous motor having a large speed control region and a large torque control region is generally used.
However, the interior permanent magnet synchronous motor may damage the battery power by high voltage due to high-speed rotation of a permanent magnet, when the motor and the inverter system break.
In detail, in the interior permanent magnet motor that is used for high-performance control, high voltage due to the permanent magnet may be generated by the rotation of the motor when a fault occurs in a normal operation at a high speed. The generated high voltage overcharges and damages the high voltage battery, which is an energy storage in the hybrid vehicle, through the inverter system, such that the durability is reduced and the life span of the battery is considerably reduced.
Further, when the system fails to prevent the overcharging, a fire due to explosion of the battery may be generated at any time, such that it is difficult to ensure safety for a driver.
In order to solve the problems due to overcharging the high voltage battery, the problem due to overcharging has been prevented in the related art by controlling the operation through a predetermined specific shifting map when the motor breaks.
That is, various types of several desired shifting maps were implemented in accordance with the conditions of a vehicle, for a variable transmission in the related art, in consideration of the fuel efficiency and the acceleration performance, such that a specific shifting map is provided to prevent overcharging due to high-speed rotation of the motor when the motor breaks in the system.
Therefore, the operation is kept in accordance with the shifting map when the motor normally operates, but upper shift or lower shift is performed by the specific shifting map when the motor breaks, thereby alleviating the problem due to overcharging, in the related art.
However, the related art of adjusting the shifting map as described above also has a problem in that excessive shifting is required and that temporal overcharging may thus be generated by excessive shifting, due to a difference between a shifting map for a normal operation and a shifting map for a fault.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.